#============================================
# 推导过程
# 第一页
# #数据类型转换
# cry:
# current_ page = int( current_ _page )
# except Exception:
# current_ page = 1
# #每页展示多少条
# per_ page_ num = 10
# #起始位置
# start_ page = (current_ page - 1) * per_ page_ num
# #终止位置
# end_ page = current_ page * per_ page_ num
# #计算出到底需要多少页3
# all_ count = book_ list. count( ) 
# page_ count, more = divmod(all_ count, per_ page_ num)
# if more:
# page_ count += 1
# page_ html =
# XXX = current_ page
# if current_ page 6
# current_ page = 6
# for i in range (current_ page-5,current_ _page+6) :
# if XXX == i:
# page_ html += '<li class="active"><a href=" ?page=8s">8s</a>
# </1i>'8(i,i)
# else:
# page_ html += '<li><a href=" ?page=8s">8s</a></1i>'8(i,i)
# book_ queryset = book_ list[start_ page:end_ _page ]
# django中有自带的分页器模块但是书写起来很麻烦并且功能太简单
# 所以我们自己想法和设法的写自定义分页器
# 上述推导代码你无需掌握只需要知道内部逻辑即可
# 我们基于上述的思路已经封装好了我们自己的自定义分页器
# 之后需要使用直接拷贝即可
#============================================
# django也有内置的分页器模块但是功能较少代码繁琐不便于使用
# 所以我们自己自定义我们自己的分页器
# 1. queryset对象是直接切片操作的
# 2.用户到底要访问哪一页如何确定?
# url?page=1
# current_ page = request. GET.get('page' ,1)
# #获取到的数据都是字符串类型你需要注意类型转换
# 3.自己规定每页展示多少条数据
# per_ page_ num = 10
# 4.切片的起始位置和终止位置
# start_ page =
# (current_ page - 1) * per_ _page_ num
# end_ page = current_ page * per_ page_ num
# #利用简单找规律找出上述四个参数的规律
# 5.当前数据的总条数
# book_ queryset . count( )
# 6.如何确定总共需要多少页才能展示完所有的数据
# #利用python内置函数divmod( )
# page_ count, more = divmod(all_ count,per_ page_ num)
# if more:
# page_ count += 1
# 7.前端模版语法是没有range功能的
# #前端代码不一定非要在前端书写也可以在后端生成传递给页面
# 8.针对需要展示的页码需要你自己规划好到底展示多少个页码
# #一般情况下页码的个数设计都是奇数(符合审美标准) 11个页码
# 当前页减5
# 当前页加6
# 你可以给标签价样式从而让选中的页码高亮显示
# 9.针对页码小于6的情况你需要做处理不能再减
# 自定义分页器推导到第九部就可以无需你继续推到了代码也无需掌握
#============================================
# class Pagination(object):
#     def __init__(self, current_page, all_count, per_page_num=2, pager_count=11):
#         """
#         封装分页相关数据
#         :param current_page: 当前页
#         :param all_count:    数据库中的数据总条数
#         :param per_page_num: 每页显示的数据条数
#         :param pager_count:  最多显示的页码个数
#         """
#         try:
#             current_page = int(current_page)
#         except Exception as e:
#             current_page = 1

#         if current_page < 1:
#             current_page = 1

#         self.current_page = current_page

#         self.all_count = all_count
#         self.per_page_num = per_page_num

#         # 总页码
#         all_pager, tmp = divmod(all_count, per_page_num)
#         if tmp:
#             all_pager += 1
#         self.all_pager = all_pager

#         self.pager_count = pager_count
#         self.pager_count_half = int((pager_count - 1) / 2)

#     @property
#     def start(self):
#         return (self.current_page - 1) * self.per_page_num

#     @property
#     def end(self):
#         return self.current_page * self.per_page_num

#     def page_html(self):
#         # 如果总页码 < 11个：
#         if self.all_pager <= self.pager_count:
#             pager_start = 1
#             pager_end = self.all_pager + 1
#         # 总页码  > 11
#         else:
#             # 当前页如果<=页面上最多显示11/2个页码
#             if self.current_page <= self.pager_count_half:
#                 pager_start = 1
#                 pager_end = self.pager_count + 1

#             # 当前页大于5
#             else:
#                 # 页码翻到最后
#                 if (self.current_page + self.pager_count_half) > self.all_pager:
#                     pager_end = self.all_pager + 1
#                     pager_start = self.all_pager - self.pager_count + 1
#                 else:
#                     pager_start = self.current_page - self.pager_count_half
#                     pager_end = self.current_page + self.pager_count_half + 1

#         page_html_list = []
#         # 添加前面的nav和ul标签
#         page_html_list.append('''
#                     <nav aria-label='Page navigation>'
#                     <ul class='pagination'>
#                 ''')
#         first_page = '<li><a href="?page=%s">首页</a></li>' % (1)
#         page_html_list.append(first_page)

#         if self.current_page <= 1:
#             prev_page = '<li class="disabled"><a href="#">上一页</a></li>'
#         else:
#             prev_page = '<li><a href="?page=%s">上一页</a></li>' % (self.current_page - 1,)

#         page_html_list.append(prev_page)

#         for i in range(pager_start, pager_end):
#             if i == self.current_page:
#                 temp = '<li class="active"><a href="?page=%s">%s</a></li>' % (i, i,)
#             else:
#                 temp = '<li><a href="?page=%s">%s</a></li>' % (i, i,)
#             page_html_list.append(temp)

#         if self.current_page >= self.all_pager:
#             next_page = '<li class="disabled"><a href="#">下一页</a></li>'
#         else:
#             next_page = '<li><a href="?page=%s">下一页</a></li>' % (self.current_page + 1,)
#         page_html_list.append(next_page)

#         last_page = '<li><a href="?page=%s">尾页</a></li>' % (self.all_pager,)
#         page_html_list.append(last_page)
#         # 尾部添加标签
#         page_html_list.append('''
#                                            </nav>
#                                            </ul>
#                                        ''')
#         return ''.join(page_html_list)

# 后端
#  def get_book(request):
#    book_list = models.Book.objects.all()
#    current_page = request.GET.get("page",1)
#    all_count = book_list.count()
#    page_obj = Pagination(current_page=current_page,all_count=all_count,per_page_num=10)
#    page_queryset = book_list[page_obj.start:page_obj.end]
#    return render(request,'booklist.html',locals())
# 前端
# <div class="container">
#     <div class="row">
#         <div class="col-md-8 col-md-offset-2">
#             {% for book in page_queryset %}
#             <p>{{ book.title }}</p>
#             {% endfor %}
#             {{ page_obj.page_html|safe }}
#         </div>
#     </div>
# </div>